A power distribution system has been known in which power sent from a power plant is converted in a power substation and supplied to a load facility of a customer such as a house or a factory. A wire connecting the power substation of an electric power provider and the load facility of the customer includes a high-voltage wire which distributes power equal to or more than a predetermined voltage and a low-voltage wire which distributes power converted by a pole transformer or the like.
Standard voltages and allowable ranges to allow a deviation from the standard voltages are defined for the high-voltage wire and the low-voltage wire. For this reason, a voltage drop is calculated by dividing the power distribution system from the power substation to the load facility into a high-voltage system containing facilities such as the high-voltage wire and a switch and a low-voltage system containing facilities such as a low-voltage wire and a lead-in wire. Then, the voltage of the power-distributed from the power substation is set such that a voltage before and after the voltage drop remains in the allowable ranges of the high-voltage system and the low-voltage system, or the voltage of the power flowing through the power distribution system is adjusted by switching an open/close state of the switch disposed in the high-voltage system.